全文获取类型
收费全文 | 2578篇 |
免费 | 228篇 |
国内免费 | 72篇 |
学科分类
生物科学 | 2878篇 |
出版年
2023年 | 22篇 |
2022年 | 24篇 |
2021年 | 61篇 |
2020年 | 38篇 |
2019年 | 58篇 |
2018年 | 54篇 |
2017年 | 59篇 |
2016年 | 65篇 |
2015年 | 133篇 |
2014年 | 132篇 |
2013年 | 160篇 |
2012年 | 201篇 |
2011年 | 193篇 |
2010年 | 115篇 |
2009年 | 105篇 |
2008年 | 136篇 |
2007年 | 116篇 |
2006年 | 122篇 |
2005年 | 92篇 |
2004年 | 108篇 |
2003年 | 91篇 |
2002年 | 97篇 |
2001年 | 84篇 |
2000年 | 73篇 |
1999年 | 53篇 |
1998年 | 29篇 |
1997年 | 25篇 |
1996年 | 32篇 |
1995年 | 14篇 |
1994年 | 22篇 |
1993年 | 19篇 |
1992年 | 26篇 |
1991年 | 18篇 |
1990年 | 31篇 |
1989年 | 20篇 |
1988年 | 24篇 |
1987年 | 13篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1984年 | 21篇 |
1983年 | 17篇 |
1981年 | 13篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 16篇 |
1976年 | 14篇 |
1975年 | 15篇 |
1974年 | 8篇 |
1972年 | 9篇 |
1969年 | 8篇 |
排序方式: 共有2878条查询结果,搜索用时 328 毫秒
1.
M N Lorenzo R Y Khan Y Wang S C Tai G C Chan A H Cheung P A Marsden 《Biochimica et biophysica acta》2001,1522(1):46-52
Generation of the functionally pleiotropic members of the endothelin vasoactive peptide family is critically catalyzed by unique type II metalloproteases, termed endothelin converting enzymes (ECE). Isolation of human ECE-2 (EC 3.4.24.71) cDNAs revealed deduced open reading frames of 787 and 765 amino acids with approximately 60% identity with human ECE-1. Characterization of mRNA variants revealed mRNA structural diversity at the 5'-terminus. Two mRNA species exist containing distinct first and second exons. Furthermore, in one of these species, an in-frame deletion of the intracytoplasmic domain removed 29 amino acids. Because of the previously reported human genetic diseases ascribed to germline mutations of member genes of the endothelin family, ECE2 was localized in human chromosomes with fluorescence in situ hybridization and radiation hybrid mapping to 3q28-q29 and SHGC-20171/D3S1571, respectively. 相似文献
2.
Nimra Khan Dylan Pelletier Thomas S. McAlear Nathalie Croteau Simon Veyron Andrew N. Bayne Corbin Black Muneyoshi Ichikawa Ahmad Abdelzaher Zaki Khalifa Sami Chaaban Igor Kurinov Gary Brouhard Susanne Bechstedt Khanh Huy Bui Jean-François Trempe 《Structure (London, England : 1993)》2021,29(6):572-586.e6
3.
4.
Dominique Grizeau Lan Anh Bui Catherine Dupré Jack Legrand 《Critical reviews in biotechnology》2016,36(4):607-618
Over the last decades, production of microalgae and cyanobacteria has been developed for several applications, including novel foods, cosmetic ingredients and more recently biofuel. The sustainability of these promising developments can be hindered by some constraints, such as water and nutrient footprints. This review surveys data on N2-fixing cyanobacteria for biomass production and ways to induce and improve the excretion of ammonium within cultures under aerobic conditions. The nitrogenase complex is oxygen sensitive. Nevertheless, nitrogen fixation occurs under oxic conditions due to cyanobacteria-specific characteristics. For instance, in some cyanobacteria, the vegetative cell differentiation in heterocyts provides a well-adapted anaerobic microenvironment for nitrogenase protection. Therefore, cell cultures of oxygenic cyanobacteria have been grown in laboratory and pilot photobioreactors (Dasgupta et al., 2010; Fontes et al., 1987; Moreno et al., 2003; Nayak & Das, 2013). Biomass production under diazotrophic conditions has been shown to be controlled by environmental factors such as light intensity, temperature, aeration rate, and inorganic carbon concentration, also, more specifically, by the concentration of dissolved oxygen in the culture medium. Currently, there is little information regarding the production of extracellular ammonium by heterocytous cyanobacteria. This review compares the available data on maximum ammonium concentrations and analyses the specific rate production in cultures grown as free or immobilized filamentous cyanobacteria. Extracellular production of ammonium could be coupled, as suggested by recent research on non-diazotrophic cyanobacteria, to that of other high value metabolites. There is little information available regarding the possibility for using diazotrophic cyanobacteria as cellular factories may be in regard of the constraints due to nitrogen fixation. 相似文献
5.
Y Y Tai J Ninomiya-Tsuji K Furuoku N Ogawa S Ishibashi K Shiroki K Segawa N Tsuchida M Shibuya T Ide 《Cell structure and function》1990,15(6):385-391
tsJT60 is a nonlethal temperature-sensitive (ts) mutant of a Fischer rat cell line (3Y1) classified as a G0 mutant; i.e., the ts defect is not expressed within the cell growth cycle but is expressed only between the G0 and S phase. tsJT60 clones transformed with oncogenes such as adenovirus E1A, polyoma large T, polyoma middle T, v-Ki-ras, and LTR activated c-myc, or with a chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine, grew well at 34 degrees C. However, most of these clones grew slowly at 40 degrees C, producing many floating dead cells, and some clones were killed at 40 degrees C. When they were cultured under conditions inadequate for growth of untransformed cells, such as high cell density or serum restriction, they were killed at 40 degrees C. These and previous results from SV40- and adenovirus-transformed tsJT60 clones favour the idea that transformed tsJT60 cells occasionally enter the G0 phase and are metabolically imbalanced at 40 degrees C during self-stimulation from the G0 to S phase. We propose that a drug which exclusively block, G0-G1 transition would be cytocidal to transformed cells but cytostatic to normal cells. 相似文献
6.
7.
8.
Dar-Fu Tai Ching-Chong Huang Hui-Yao Huang Ing-Lung Shih 《Biotechnology letters》1993,15(12):1229-1232
Summary Enzymatic hydrolysis of racemic 3-acetylthio-2-methylpropionic methyl ester catalyzed by bovine pancreatic protease and Mucor javanicus lipase showed opposite enantioselecivity. A tandem hydrolysis of the ester catalyzed by these two enzymes gives enantiomerically enriched (S)-3-acetylthio-2-methylpropionic acid, a building block of captopril. 相似文献
9.
10.
Yoko Yamauchi Hikari Kimoto Xianyu Yang Sergey Filkin Yuri Utkin Tai Kubo 《Bioscience, biotechnology, and biochemistry》2016,80(1):158-161
Three-finger toxins (3FTxs) are one of the major components in snake venoms. In this study, we isolated a cDNA encoding a short-chain 3FTx, Pr-SNTX, from Pseudechis rossignolii. The amino acid sequence of Pr-SNTX is nearly identical to that of its ortholog in Pseudechis australis. Pr-SNTX protein inhibited muscle-type (α2βδε), but not neuronal α7 nicotinic acetylcholine receptor (nAChR) activity. 相似文献